Many processes for remediating unwanted materials from underground zones require sampling of underground vapors and analysis of the sampled vapors. Periodic sampling can be required to control the remediation process, e.g., to assure the availability of oxygen in a vadose zone above a water table during a bioremediation process. Typically, underground vapor samples are brought to the surface, and a gas chromatograph (GC) is used to analyze the gas or vapor constituents. In some applications, vapor sampling must be accomplished frequently to optimize performance.
However, frequent vapor sampling and analysis are costly. In addition, GC equipment may have to be protected from liquids in vapor samples since an underground location which is normally unsaturated may become saturated with water or other liquids during the remediation process. Although placing continuous sensors of a vapor constituent could be cost effective in at least some remediation applications, the repeatability or accuracy of continuous sensors (e.g., electrochemical, PID, or catalytic types, has not proven to be acceptable in these underground remediation applications. These continuous sensors are especially unreliable after being exposed to liquid saturated conditions. Other problems with current sampling methods and devices include unacceptable response times and delayed readouts.